The invention relates to measuring and recording apparatus particularly for use in testing and maintaining electrical domestic appliances operating at a temperature different from the ambient temperature, typically refrigerators and washing machines.
There exist numerous types of measuring apparatus which generally comprises individual units, such as current meters, voltmeters, counters, wattmeters and thermometers. Continuous monitoring by a technician is required during use. Substituting optically readable instruments with recording instruments, for instance of the type disclosed in "Technische Rundschau" Vol. 66, No. 33, pp. 19-20, cannot be regarded as a definite improvement, since later reading of a recorded strip corresponding to the whole duration of an operating cycle is a time consuming operation, particularly when the operating cycle is rather long.
It is an object of the invention to provide an improved measuring and recording apparatus suitable for shop test maintenance and/or repair of electrical domestic appliances operating in accordance with a predetermined cycle.
It is a more specific object to provide an apparatus which is of relatively low cost and versatile in use and which makes it possible to spare working hours by removing the need for continuous attendance during tests and visual inspection of a recorded strip corresponding to the whole time duration of the cycle.
Still another object of the invention is to render the apparatus operable to provide a record of the variations of the relevant parameter(s) during an operating cycle of a domestic electric appliance operating at a temperature which is different from the ambient temperature without attendance, while visual monitoring remains possible and recording occurs only during predetermined portions of the cycle.
It is a secondary object to render the apparatus adaptable to fairly different types of domestic appliances, and particularly to those machines which operate at a temperature in excess of the ambient temperature (electric ovens, electrical cloth and dish washing machines) and those for lowering the temperature within an enclosure (refrigerators, and deep freeze machines).
According to the invention, there is provided an apparatus having an housing locating a multiscale electrical current recorder and a digital thermometer, as well as an electronic circuit. The recorder is associated with a current probe for connection to a circuit to be monitored (i.e. the power circuit of the machine to be tested) and to a temperature probe. Memory means are operable to store the temperature level responsive to a predetermined event (for instance the maximum value of the temperature). The electronic circuit is designed for rendering the recorder operative to record the electrical current in the circuit to be monitored when that current exceeds a predetermined value.